PRINCIPLES OF VETERINARY SURGERY 459 



longed action of the liquids of a refractory animal. The 

 serum is therefore not a bactericide. It is only antitoxic 

 and its preventive action is due, not to the destruction of 

 the bacillus, but to the neutralization of its poison. Roux, 

 Vaillard and Nocard, in 1893, had completed the study of 

 antitetanic serum, and had indicated the mode of preparation 

 and direction for its use in practice. 



PREPARATION OF ANTITETANIC SERUM.— The 

 horse is used for the preparation of antitetanic serum be- 

 cause it is capable of supplying a considerable quantity of 

 blood; because of the limited natural toxicity of its serum, 

 and because of the facility with which it can be injected and 

 bled. 



The animal is first vaccinated by subcutaneous iiijections 

 of an eighth or a quarter of a cubic centimeter of toxin mixed 

 with a few drops of solution of iodine. An injection is made 

 every four or five days, and the dose is gradually increased. 

 The injections are made subcutaneously. They cause a lit- 

 tle local swelling, but not general disturbances. Later, when 

 the blood has become antitoxic, the injections may be begun 

 with pure toxin, but in small doses, and at intervals of nine 

 days. Again, these doses are gradually increased until the 

 horse is able to withstand 30 to 40 cubic centimeters of pure 

 toxin. Henceforth the dose is more rapidly increased until 

 200 to 300 cubic centimeters of very active toxin is injected 

 in a single dose. 



At the end of some months the horse is sufiliciently im- 

 munized to warrant a trial of its serum. If the blood is 

 found insufficiently antitoxic the injections are continued af- 

 ter an interval of ten days rest. When the desired antitoxic 

 potency has been obtained, from five to six litres of blood 

 are drawn from the jugular vein. The blood-letting is done 

 with a sterilized trocar inserted into the vein from below 

 upwards, and attached to a rubber tube connected with a 

 flask in which the separation of the serum is to be effected. 



